[Attention Surplus Disorder]

Think I found the solution:

http://www.techsupportalert.com/content/how-stop-firefox-stealing-window-focus.htm

How To Stop Firefox From Stealing Window Focus
Updated 19. September 2011 - 6:32 by rhiannon

Prevent Firefox from opening when you’re doing other things

Firefox turned 5 this week. While no other browser to date has been able to lure me away from Firefox since its first early beta, it does have its flaws and frustrations.
One of the most annoying habits Firefox has is stealing the focus from other programs you are working in. Clicking on a hyperlink inside programs such as email or office type applications causes the link you clicked on to automatically open inside Firefox. For example, I’m reading email, and I click on a link inside the email. All of a sudden I’m looking at a Firefox window showing the web page that the email link goes to.

[Attention Surplus Disorder]

False alarm, the above didn’t work.